This invention relates to dental implements and, more particularly to dental implements which are particularly designed for the filling of root canals with sealing materials.
There are several methods of sealing root canal systems, and most of them using a rubber-like material called gutta percha. This gutta percha may be in the form of a tapered cone, which is compacted into the root canal with pluggers. Alternatively, the gutta percha may be placed as a coating on an obturating carrier, which is warmed to soften the gutta percha, and deposited in the root canal where the carrier compacts the material into the canal space.
Currently, the shapes of filling materials and obturating carriers do not match the tapering shapes of prepared root canals. When the step-back technique of canal shaping is used, the final shape of the canal preparation can only be discerned indirectly by the increments that each larger instrument fits further back from the terminus of the canal, a difficult skill learned only after much experience. As the prepared taper is often obscure to the clinician, it is likewise difficult to pick an appropriately tapered gutta percha point or obturating carrier with which to seal the canal. If the selected obturating device or gutta percha point is too tapered, it will bind in the canal short of the canal's terminus, causing the crucial apical seal to be inadequate and allowing leakage and failure of the endodontic treatment. If the obturating device or gutta percha point is too narrow, little hydraulic pressure will be exerted on the filling material in the cervical two-thirds of the canal during condensation procedures and lateral or accessory canals in that region of the canal may not be sealed, again increasing the chance for failure of the endodontic treatment.
While there are many techniques of filling root canals, it is generally recognized in the field of endodontics that those methods which warm and soften the gutta percha filling material, thereby allowing it to be thoroughly compacted into all the nooks and crannies of root canal systems, are superior to those techniques which do not thermoplasticize the gutta percha prior to condensation.
Vertical condensation of warm gutta percha is a known technique for warming and compacting gutta percha in a root canal (see e.g. U.S. Pat. No. 5,406,053). In this technique, an appropriately tapered gutta percha cone is fit and cemented in the prepared root canal, and a flame-heated or electrically-heated gutta percha heat carrier is used to sear off the gutta percha cone at the orifice level of the canal. Pressing the softened gutta percha into the canal with an appropriately sized vertical condensation plugger initiates the first wave of condensation, filling any lateral canals present in that region in the primary canal. The heat carrier is then reintroduced into the canal in order to penetrate the gutta percha several millimeters (mm), heat the apical mass, and remove a portion of the apical mass so that the next wave of condensation may occur deeper in the root. These heating and compacting cycles continue until the final wave of condensation which ends approximately five to seven millimeters from the canal terminus.
It generally takes from three to seven waves of condensation to reach this end point. At the end point, the clinician must either place a retentive post in the coronal canal space or backfill it with gutta percha. Backfilling can be done by heating small pieces of gutta percha and sequentially packing them into the canal or by syringing alloquates of pre-heated gutta percha from a gutta percha gun and compacting them with pluggers. Downpacking with multiple waves of condensation and backfilling in the manners described require at least seven different instruments, fairly extensive training of the clinician and chairside assistant, and between fifteen and thirty minutes of clinical time. Furthermore, these condensation pluggers and heat carriers lack a correlating mechanism to match their sizes to the taper of the canal preparation.
In the preparation of a root canal by removing the pulp and shaping the canal to the best configuration for receiving filling materials, such as gutta percha, it is extremely important to control the depth of penetration of root canal files and to limit the depth of penetration to the root tip.
Obturation condensation devices, often referred to as pluggers or, if provided with heating elements as heat carrier/pluggers, are designed for the insertion and packing of tapered gutta percha cones into a previously prepared root canal. For example, U.S. Pat. No. 5,921,775, herein incorporated by reference, describes an endodontic treatment system in which the shaping instruments, irrigation cannulas, filling implements, and related materials are designed to safely create specific tapers in root canal preparation. All of the identified implements are designed with the same taper, preferably one which is greater than the standard ISO taper of 0.02 mm of taper/mm of flute length.
When an electric heat plugger is used to downpack or condense the thermo-plasticized gutta percha into the apical and lateral canal spaces, the gutta percha that moves along the side of the plugger is usually removed after the downpack is completed, leaving the coronal canal space empty. A second obturation device called a gutta percha backfilling syringe is required to backfill the empty space. Gutta percha backfilling syringe needles are typically made of sterling silver or a silver alloy because heat conduction from the syringe heating chamber to the end of the syringe needle must be adequate to keep the temperature of the gutta percha material high enough to remain thermo-plastic along the entire length of the needle to its tip. However, syringe needles made of silver or silver alloys lack the inherent rigidity to be used to condense the thermo-plasticized material into the root canal space after they have heated and extruded said material into the canal space.
As a result, there is a need for a backfilling syringe needle that can conduct heat from the syringe heating chamber to the tip of the needle while maintaining sufficient rigidity to pack the warmed gutta percha into the canal space. There is also a need for a needle that eliminates the need to fit tapered gutta percha master cones or carriers into the root canal and reduces the typical device set of a downpacking electric heat plugger and a gutta percha backfilling syringe into a single device.